1. Field of the Invention
The present invention relates to a method of producing a semiconductor device, and more particularly to a method of forming closely spaced electrodes connected to various semiconductor regions.
2. Description of the Prior Art
During manufacture of semiconductor devices, it is necessary to form electrodes connected to various semiconductor regions and it is sometimes desirable to form electrodes as close together as possible, such as for high frequency operation or for decreasing the occupying area of the circuit elements in an integrated circuit, etc.
In prior art photoetching techniques, however, a minimum distance of 5-10.mu. between electrodes is necessary due to the limitations of mask registration precision and photoetching precision.
For example, in the manufacture of a bipolar transistor, as illustrated by a sectional view in FIG. 7 of the drawings, the distance d between emitter electrode 7 and base electrode 8 must be approximately 5-10.mu. due to the limitations on the mask registration precision and photoetching resolution precision; hence, base region 4 must be made larger than is necessary in order to take into account inaccuracies in mask registration and photoetching.
Similarly, in the manufacture of a diffused resistor, as illustrated in the sectional view of FIG. 8, there is a minimum distance d between the two contacts 7 and 8 for the reasons discussed above. Accordingly, in order to form a diffused resistor having a low resistance with such limitations, it is necessary to enlarge the width of the diffused region. Thus, the degree of integration must be sacrificed, so that, in addition to the lowering of the degree of integration, the problem of increase in the parasitic capacitance is involved.
Similar problems also occur in the manufacture of junction capacitors and junction type field effect transistors.